Method, network and control station for the two-way alternate control of radio systems of different standards in the same frequency band

ABSTRACT

The invention relates to an interface-control protocol method for a radio system, which has at least one frequency band provided for the two-way alternate utilization of a first and a second radio interface standard. The radio system comprises a number of stations, which each function in accordance with a first radio interface standard and/or in accordance with a second radio interface standard, in which a control station is provided that controls the two-way alternate utilization of the frequency band.

The invention relates to a method of alternate control of radio systemsof different standards in the same frequency band.

A radio system for wireless transmission of information is allowed touse transmission power only in accordance with standards. The nationalregulation authority determines on what frequencies with whattransmission power and in accordance with what radio interface standarda radio system is allowed to transmit. For this purpose there isprovided for so-termed ISM frequency bands (Industrial ScientificMedical) that radio systems transmit in the same frequency band inaccordance with different radio interface standards. An example of thisis the US radio system IEEE802.11a and the European ETSI BRANHiperLAN/2. The two radio systems transmit in the same frequency bandsbetween 5.5 GHz and 5.875 GHz with approximately the same radiotransmission method, but different transmission protocols.

In the event of interference, method were standardized for an activeswitching to another frequency within the permitted frequency band, forcontrolling transmission power and for the adaptive coding andmodulation to reduce interference. Radio systems of wideband LANs of theradio interface standards ETSI BRAN HiperLAN/2 and IEEE802.11a utilizethe same radio transmission method, a 64-carrier OFDM method and anadaptive modulation and coding. About the same modulation and codingmethods (Link Adaptation, LA) are defined for the two standards.

The Medium Access Control (MAC) of the two systems is totally different.ETSI BRAN HiperLAN/2 utilizes a centrally controlled reservation-basedmethod in which a radio station takes over the role of a centralinstance co-ordinating the radio resources. This central radio station(Access Point, AP) which may be an access point to the wide areanetwork, periodically signals every 2 ms the MAC frame structure fromthe AP and the associated stations if required.

The IEEE802.11a standard describes a CSMA/CA (Carrier Sense MultipleAccess/Collision Avoidance) method not based on reservations, in whichall the radio stations listen in on the medium and assume that thechannel is unused for a minimum duration (Short InterFrame Space, SIFS)before 802.11a-MAC frames, thus user data packets, are transmitted ifnecessary. The method is highly suitable for self-organizing ad hocnetworks, but requires positive acknowledgements of all the packets.Measures supporting service quality (Point Coordination Function PCF) inaddition allow the support of multimedia applications. FIG. 2 shows byway of example the sequence for media access in accordance withIEEE802.11a. In accordance with a variant of the standard a station isto then transmit an RTS packet (Ready To Send) and wait for a CTS packet(Clear To Send) from the addressed station before it is allowed totransmit user data. All the other stations in the radio coverage areaset a time monitoring (Network Allocation Vector, NAV) and do nottransmit until the addressed station has sent an acknowledgement(ACKnowledge, ACK).

Wideband LANs in accordance with the HiperLAN/2 and 802.11a standardswill operate in the same frequency band in the future between 5.15 and5.825 GHz. The wideband LANs work with Transmitter Power Control (TPC),it is true, with adaptive radio transmission methods and the DynamicFrequency Selection (DFS) to minimize the alternating interferingeffects, these methods, however, do not make optimum use and spreadingpossible of the radio channels over the stations which transmit inaccordance with different standards. The guarantee of the servicequality necessary for the multimedia applications is impossible in thecase of interference caused by their own stations or stations of outsidesystems. In case of alternating interference, systems do not workefficiently and occupy a frequency channel even at low transmissionrates.

It is an object of the invention to provide a method, a wireless networkand a control station which make efficient use of radio transmissionchannels possible.

This object is achieved for the method in accordance with the inventionby an interface control protocol method for a radio system, which systemcomprises at least a frequency band provided for the alternate use of afirst and a second radio interface standard, the radio system comprisingstations which operate in accordance with a first radio interfacestandard and/or a second radio interface standard, respectively, acontrol station being provided which controls the alternate use of thefrequency band.

The invention is based on the idea of providing a comprehensive standardexchange of implicit or explicit control information in systems thathave the same radio transmission methods but different radiotransmission protocols. This makes a simple and efficient use possibleof a radio channel via a plurality of radio interface standards.

The radio system comprises one or more stations. The stations may be,for example, computers of a wireless local area network. These stationsmay be arranged, for example, only for operation in accordance with afirst or second radio interface standard. But it is also possible forstations to operate in accordance with both the first and the secondradio interface standard.

A first number of stations preferably forms a wireless local areanetwork in accordance with a first radio interface standard and a secondnumber of stations forms a wireless network in accordance with a secondradio interface standard. The first radio interface standard may be, forexample, the HiperLAN/2 standard and the second radio interface standardmay be the IEEE802.11a standard.

For these two standards is reserved the frequency band from 5.15 GHz to5.825 GHz.

In accordance with the invention a control station is provided whichcontrols the alternate use of the common frequency band of the two radiointerface standards.

The control station is preferably a station that may operate inaccordance with both the first and the second radio interface standard.

The control of the alternate use of the common frequency band may beeffected in various ways. For example, it is possible to provide certainpredefinable time intervals for the use of the first and second radiointerface standard and allocate the frequency band alternately to thefirst radio interface standard and then to the second radio interfacestandard in a kind of time-division multiplex mode.

However, it is advantageous to effect the allocation by means ofadaptive protocols. The common radio channel can then be utilized moreeffectively particularly when the demand for transmission capacity inaccordance with the first and the second radio interface standardvaries.

In the advantageous embodiment of the invention as claimed in claim 2,the control station is provided, on the one hand, for controlling theaccess to the frequency band for stations operating in accordance withthe first radio interface standard. If the first radio interfacestandard is, for example, the HiperLAN/2 standard, the control stationperforms the function of the central controller (Access Point AP) inaccordance with this standard. In that case the stations of theHiperLAN/2 standard send a request for capacity to the control stationand the control station allocates transmission capacity to eachrespective station.

On the other hand, the control station is provided in an advantageousembodiment of the invention as claimed in claim 2 for releasing thecommon frequency band for access by stations operating in accordancewith the second radio interface standard, if stations operating inaccordance with the first radio interface standard do not request accessto the frequency band. In this advantageous embodiment of the inventionthe first radio interface standard is given priority over the secondradio interface standard in this manner. The release of the commonfrequency band for the second radio interface standard may be effected,for example, explicitly by the sending of control information to thestations of the second radio interface standard.

Alternatively, it is possible, for example, that the point coordinatorprovided in accordance with the IEEE802.11a standard operates as thecentral control station and controls the alternate access of stations ofthe first and second radio interface standard to the common frequencyband. In this advantageous embodiment of the invention the pointcoordinator could for example periodically render the common frequencyband available to another radio interface standard, for example, to theHiperLAN/2 standard.

In the advantageous embodiment as claimed in claim 3, the control iseffected in that the control station determines the respective durationin which the stations operating in accordance with the second radiointerface standard can utilize the common frequency band. Determiningthe duration may advantageously be effected as claimed in claim 4 inthat the control station sends a broadcast signal which informs thestations of a time period in which the frequency band can be used bystations operating in accordance with the second radio interfacestandard.

It is an advantage of the invention that when radio systems are operatedin phases in which no information is sent or received by a radio stationin accordance with a first radio interface standard, the additionalsending of information in accordance with another radio interfacestandard becomes possible, so that the access to the radio channel canbe controlled by competing radio systems.

It is then possible for a first radio station operating in accordancewith a first radio interface standard to additionally carry out certainfunctions described in a second radio interface standard, while thefirst radio station or a coordinating further radio station thattransmits in accordance with the first radio interface standarddetermines the beginning and duration of the phase that may be used bythe first station for transmission in accordance with the second radiointerface standard.

Depending on the radio interface standard, beginning and duration can bedefined only approximately, while the respective standards are violatedregularly or from time to time. The first station may preferably end thephase during which it transmits in accordance with the second radiointerface standard, while disregarding resulting interference instations operating in accordance with the second radio interfacestandard.

The first radio station may, in addition to functions in accordance withthe second radio interface standard, also carry out functions that causeradio systems working in accordance with the second radio interfacestandard or radio systems working in accordance with the first radiointerface standard to interpret the radio channel as interfered andoccupy another radio channel for its own operation.

The efficient common use of a radio channel by different radio systemsmay be achieved via a suitable control protocol method. Such a radiointerface control protocol method enables a first station of a radiosystem working in accordance with the first radio interface standard tocontrol the access times to the radio channel by other stations. Forthis purpose this first station then has to carry out functionsdescribed in another, second radio interface standard in addition to thefunctions laid down by its own first radio interface standard at timesat which stations working in accordance with the first radio interfacestandard do not send and do not expect information in accordance withthe standard from the first station, while the first station or afurther station determines the duration for which the first station isallowed to transmit in accordance with the second radio interfacestandard. The duration of the operation in accordance with the secondradio interface standard need not be determined exactly but may also bedetermined approximately. A transmission in accordance with the firstradio interface standard can provide that the first station terminatesthe use of the radio interface in accordance with the second radiointerface standard without taking resulting interference into account instations that send in accordance with the second radio interfacestandard.

The object of the invention is achieved for the network by a wirelessnetwork that has at least one frequency band that is provided for thealternate use by a first and a second radio interface standard, whilethe wireless network comprises stations that work in accordance with thefirst and/or the second radio interface standard, a control stationbeing provided which controls the alternate use of the frequency band.

Several examples of embodiment of the invention will be furtherexplained below with reference to the drawing in the FIGS. 1 to 3, inwhich:

FIG. 1 shows the frame structure in accordance with the ETSI BRANHiperLAN/2 standard,

FIG. 2 gives a diagrammatic representation of the access to a radiochannel in systems in accordance with the IEEE802.11a standard, and

FIG. 3 shows two wireless local area networks in accordance with a firstand a second radio interface standard.

FIG. 1 shows the structure of the HiperLAN/2-MAC frame.

FIG. 2 diagrammatically shows the media access in systems working inaccordance with the radio interface standard IEEE802.11a.

In a HiperLAN/2 system the central controller can be controlled via theAccess Point (AP) which periodically generates the MAC frame and thentransmits the data of the broadcast phase to individually control theservice quality (packet delay sending rate and so on) of individuallinks.

Transmission in FIGS. 1 and 2 with respect to the associated standardsis understood to mean that a HiperLAN/2 AP in a partially unuseddownlink, uplink and direct-mode phase could dispense with sendinguseless (dummy) information and giving 802.11-systems no opportunity toobserve an unused channel for a period of time SIFS and starting the runas shown in FIG. 2. The AP could readily regain the control in which thetransmission in accordance with the HiperLan/2 standard does notsuppress the broadcast phase, but transmission takes place. Likewise,the function PCF of the 802.11 standard could be used to occasionallyrender the radio channel available to HiperLAN/2 systems with a timelimit (periodically).

The alternate control of radio systems of different standards, whichcontrol is proposed here and discussed with respect to an example of thewideband LANs ETSI BRAN HiperLAN/2 and IEEE802.11a, may guarantee in aheterogeneous environment in which various radio systems simultaneouslytransmit very close together in the same spectrum, a decentrallycontrolled adaptivity relative to the transmission capacity available inthe respective systems for the management of the respective currenttraffic supply, of the required service quality and of the environmentof use. When the integrated controller in accordance with the inventionis used, different radio systems may be made compatible in the way thatthey constructively coexist in the same frequency band and then canprovide services that require a high service quality. The radio spectrumis clearly used more efficiently; without the implementation of the newmethod this is only possible with respective exclusively used radiochannels.

FIG. 3 diagrammatically shows two wireless local area networks.

A first wireless local area network comprises three stations 10, 11 and12. These three stations 10, 11 and 12 work in accordance with the firstradio interface standard A, for example, in accordance with theHiperLAN/2 standard.

A second wireless local area network includes four stations 14, 15, 16and 17. These four stations 14, 15, 16 and 17 work in accordance withthe second radio interface standard B, for example, in accordance withthe IEEE802.11a standard.

The stations may be, for example, computers which include a radiointerface. The communication between the individual stations is effectedin a wireless fashion, for example, by radio.

For wireless local area networks in accordance with the HiperLAN/2 andIEEE802.11a standards the frequency band is comprised between 5.15 GHzand 5.825 GHz.

A central control station 13 is provided which controls the alternateaccess by the first wireless network and the second wireless network tothe common frequency band.

This may be effected in an advantageous manner in that the station 13sends a broadcast message to the stations 14 to 17 of the IEEE802.11astandard when the stations 10 to 12 do not need transmission capacity.This broadcast message preferably contains time information whichinforms the stations 14 to 17 of the IEEE802.11 standard how long theyare allowed to utilize the common frequency band. During this time thecontrol station 13 can also carry out functions in accordance with theIEEE802.11a standard, for example, also be used for data transmission inaccordance with the IEEE802.11a standard.

If the stations 10 to 12 of the first wireless network are HiperLAN/2stations, the control station 13 preferably also operates as the centralcontrol station (Access Point) of the HiperLAN/2 network andco-ordinates its radio resources. In HiperLAN/2 systems it is plannedbeforehand at what time the stations are allowed to send. For thispurpose the HiperLAN/2 systems have a central controller (Access Point,AP) which receives the requests for capacity from the various stationsand assigns capacity accordingly. The central control station 13 ispreferably also provided for carrying out the function of the accesspoint of the HiperLAN/2 standard. The central control station 13 thenperiodically signals every 2 ms the MAC frame structure in accordancewith the requirements of the individual stations of the HiperLAN/2network.

Alternatively, it is also possible, however, in HiperLAN/2 systems forthe function of the access point and the function of the alternatingcontrol of the access to the common frequency band by the first wirelessnetwork and the second wireless network to be realized in separatestations. In that case, however, with respect to the duration in whichthe frequency band can be utilized by the first or second radiointerface standard a data exchange is necessary between these separatestations.

Alternatively, it is possible, for example, for the point co-ordinatorprovided in accordance with the IEEE802.11 standard to operate as acentral control station and to control the alternate access to thecommon frequency band by stations of the first and second radiointerface standards. In this embodiment the point co-ordinator would,for example, periodically render the common frequency band available toanother radio interface standard, for example, to the HiperLAN/2standard.

1. An interface-control protocol method for a radio system which has atleast one common frequency band that is provided for alternate use by afirst and a second radio interface standard, the radio systemcomprising: stations which operate in accordance with a first radiointerface standard and/or a second radio interface standard, and acontrol station which controls the alternate use of the frequency band,wherein the control station controls the access to the common frequencyband for stations working in accordance with the first radio interfacestandard and—renders the frequency band available for access by thestations working in accordance with the second radio interface standardif stations working in accordance with the first radio interfacestandard do not request access to the frequency band.
 2. The method asclaimed in claim 1, herein the control station determines the respectiveduration in which the stations working in accordance with the secondradio interface standard are allowed to utilize the frequency band. 3.The method as claimed in claim 1, wherein the control station sends abroadcast signal informing the stations of a time duration in which thecommon frequency band can be used by stations working in accordance withthe second radio interface standard.
 4. The method as claimed in claim2, wherein the duration of operation in accordance with the first andsecond radio interface standards is laid down only approximately whilethe respective standards are violated regularly or from time to time. 5.The method as claimed in claim 1, wherein the control station alsocarries out functions which cause radio systems in accordance with thefirst radio interface standard to interpret the radio channel asinterfered and to seize another radio channel for its own operation. 6.An interface-control protocol method for a radio system which has atleast one common frequency band that is provided for alternate use by afirst and a second radio interface standard, the radio systemcomprising: stations which operate in accordance with a first radiointerface standard and/or a second radio interface standard, and acontrol station which controls the alternate use of the frequency band,wherein the control station terminates the use of the radio interface inaccordance with the second radio interface standard by transmitting inaccordance with the first radio interface standard, without takingaccount of resulting interference in stations working in accordance withthe second radio interface standard.
 7. An interface-control protocolmethod for a radio system which has at least one common frequency bandthat is provided for alternate use by a first and a second radiointerface standard, the radio system comprising: stations which operatein accordance with a first radio interface standard and/or a secondradio interface standard, and a control station which controls thealternate use of the frequency band, wherein the control stationcontrols the access to the common frequency band by stations working inaccordance with the first radio interface standard and in that durationand type of control of the radio interface in accordance with the secondradio interface standard is determined by a further station andtransmitted to the control station.
 8. An interface-control protocolmethod for a radio system which has at least one common frequency bandthat is provided for alternate use by a first and a second radiointerface standard, the radio system comprising: stations which operatein accordance with a first radio interface standard and/or a secondradio interface standard, and a control station which controls thealternate use of the frequency band, wherein the control station, inaddition to functions in accordance with the second radio interfacestandard, also carries out functions which cause radio systems inaccordance with the second radio interface standard to interpret theradio channel as interfered and to seize another radio channel for itsown operation.
 9. A wireless network comprising at least one commonfrequency band provided for alternate use by a first and a second radiointerface standard, the wireless network comprising: stations which workin accordance with a first radio interface standard and/or in accordancewith a second radio interface standard, and a control station whichcontrols the alternate use of the common frequency band, wherein thecontrol station controls the access to the common frequency band forstations working in accordance with the first radio interface standardand—renders the frequency band available for access by the stationsworking in accordance with the second radio interface standard ifstations working in accordance with the first radio interface standarddo not request access to the frequency band.